pdfConvertPDFToWindowCoords2

XpdfViewer functions deal with two different coordinate spaces. In the
window coordinate space, (0,0) is the upper-left corner of the window,
and the units are pixels. In the PDF coordinate space, the origin is
determined by the PDF file (and may even change from page to page),
and the units are points (1 point = 1/72 inch).

This function converts a point from PDF coordinates
(page, pdfX, pdfY) to window
coordinates (returned in *winX, *winY).